In a mobile bearer network, in addition to requirements of a time division multiplexing (TDM) service, a synchronization reference source needs to be provided for a radio base station. A wireless cellular communications system includes a frequency division duplex (FDD) system and a time division duplex (TDD) system. Cells need to keep frequency synchronization in the TDD system, because a same frequency band needs to be used during uplink and downlink communication, cells in an entire network also require strict time synchronization, so as to avoid interference between uplink and downlink transmission. In the FDD system, uplink and downlink are distinguished from each other by using different frequency bands, and although it is not required to distinguish uplink from downlink by time, cells require strict time synchronization, so as to support characteristics, such as a cell handover, multicast, and broadcast. When a user is handed over between base stations, if the base stations do not perform time synchronization, it may cause a channel establishment failure, which affects a handover success rate.
In the prior art, a network-wide clock synchronization method based on the Institute of Electrical and Electronics Engineers (IEEE) 1588 Time Transfer Protocol is provided. In this method, a time source is deployed at a location of a gateway (GW) or a building base band unit-center (BBU-center), and is injected by using the Global Positioning System (GPS), the BeiDou Navigation Satellite System, an atomic clock, or the like; a bearer switching device transfers, according to the IEEE 1588 protocol, a master clock maintained by the time source. However, a synchronization transfer solution in a radio access network that is implemented based on this method is affected by factors, such as stability of a crystal oscillator, precision of a timestamp, asymmetry of a path and a component, a frequency offset of a TC, a filtering algorithm, and a clock path length, which causes low time synchronization precision.